Trace levels of perfluoroalkanoic acid impurities may occur in intermediates used in the manufacture of fluorinated alcohols. It is desirable to limit formation of these impurities in fluorinated intermediates and also during the manufacture of various polymer products using such intermediates. Furthermore, it is also desirable to eliminate or significantly reduce the occurrence in fluorinated intermediates and polymer products of potential perfluoroalkanoic acid precursors, such as their esters with 2-perfluoroalkylethyl alcohols, and perfluoroalkyliodides. Both these classes of compounds can be readily degraded by hydrolysis and/or oxidation to form perfluoroalkanoic acids.
Fluorinated alcohols are widely used as intermediates to prepare water and oil repellents, as well as soil and stain release compositions for both hard- and soft-surfaced substrates. Such substrates include building materials, such as architectural stone and tile; textiles and fabrics from natural and synthetic fibers used in apparel and carpet; as well as other surfaces. Fluorotelomer alcohols are a particular class of fluorinated alcohols used in these applications. Fluorotelomer alcohols can be prepared industrially by multiple processes that include: telomerization of pentafluoroethyliodide with tetrafluoroethylene to yield perfluoralkyliodides F(CF2CF2)nI; reaction of these perfluoroalkyliodides with ethylene to provide 1-iodo-1H,1H,2H,2H-perfluoroalkanes having the structure F(CF2CF2)nCH2CH2I; followed by hydrolysis to yield 1H,1H,2H,2H-perfluoroalkan-1-ols, F(CF2CF2)nCH2CH2OH.
In U.S. patent application 2003/125421 Bladel et al. disclose a process for the recovery of highly fluorinated carboxylic acids useful as emulsifiers from fluoropolymer dispersions. Processes for the recovery of fluorinated acids from product streams do not destroy the fluorinated acids, and may leave a significant residue of the acid in the extracted liquid product.
Japan patent application 2003/267900 describes a process for the decomposition and removal of water-soluble fluorine-containing carboxylic acids, having the fluorocarbon chain interrupted by oxygen or nitrogen, when dissolved in water at temperatures of 200° C. or less in 24 hr. Perfluoroalkanoic acids (especially their more thermally stable linear isomers) and their esters are substantially more stable under these reaction conditions and are relatively insoluble in water. This process would not selectively remove perfluoroalkanoic acids, their esters and perfluoroalkyliodide impurities from fluorinated alcohols.
It is therefore desirable to develop processes that remove perfluoroalkanoic acids, their esters, and perfluoroalkyliodides from fluorinated alcohols. The present invention provides such a process.